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A method-level @template T is replaced by its bound when the argument's @implements binding is forwarded through an abstract class with an extra, unforwarded class template #77
Description
Observed under v0.10.3
/**
* @template T of PBase
* @template U of PBase
*/
interface Q10BoxInterface {}
/**
* @template TSelf of Q10eAbstract
* @template T of PBase
* @template U of PBase
* @implements Q10BoxInterface<T,U>
*/
abstract class Q10eAbstract implements Q10BoxInterface {}
/** @extends Q10eAbstract<Q10eConcrete,PA,PB> */
final class Q10eConcrete extends Q10eAbstract {}
final class Q10dGenericCreateShape
{
/**
* @template T of PBase
* @template U of PBase
* @param Q10BoxInterface<T,U> $dto
*/
public function __construct(protected readonly Q10BoxInterface $dto) {}
}
new Q10dGenericCreateShape(new Q10eConcrete());Actual:
Q10dGenericCreateShape::__construct(): Argument $dto expects Q10BoxInterface<invariant PBase>, but Q10BoxInterface<PA> was given
The given type is resolved with a single type argument (<PA>, U dropped) and the method template falls back to its bound, checked invariantly. The trigger is the extra leading TSelf template on the abstract class: the same chain without it (variant f, @extends Q10fAbstract<PA,PB>) passes, a direct @implements Q10BoxInterface<PA,PB> on the argument's class (variant d) passes, and the chained argument against a non-templated @param Q10BoxInterface<PA,PB> (variant g) passes.
Expected: T = PA, U = PB inferred from the argument, as PHPStan resolves the @extends → @implements chain; the call is accepted.
Activity
rcalicdan commentedon Sep 18, 2026
@klunejko This issue is happening because of Positional Index Shift of Template Parameters.. I will create a dedicated PR for this..